In general, fusible resistors are used to protect circuit elements of electronic devices. A fusible resistor functions as an ordinary resistor at normal loads, but as circuit breakers in an abnormal, overload state, due to its fusible characteristics.
Conventional fusible resistors are fabricated by coating a resistor body with a thin film made of a compound consisting of carbon, tin-nickel, and nickel-chrome by electroless plating and by performing a spiral cut on the surface of the coated resistor body (hereinafter, the spiral cutting will be referred to as “trimming”). While inexpensive fabrication of conventional fusible resistors is possible, manufacturing a fusible resistor with a resistance lower than 0.1 Ω is difficult due to limitations of the manufacturing process. Further, fabricating a fusible resistor with a resistance below 0.22 Ω is very difficult since the trimming causes an increase of the resistance of the fusible resistor.
Where a current exceeding a predetermined range flows through the circuit of an electronic device, a conventional fusible resistor generates excessive heat. To overcome this drawback, increasing the rated current of a fusible resistor or using a micro fuse instead of the fusible resistor have been proposed. However, increasing the rated current results in an increase of the size of the fusible resistor. Further, using a micro fuse is not cost effective because mass-production of micro fuses is limited due to the structural characteristic of a micro fuse and expensive raw materials required.